Alfred Werner 1179565 224266813 2008-07-08T02:01:34Z Numbo3-bot 7118326 robot Modifying: [[ar:ألفرد فيرنر]] {{Infobox_Scientist |name = Alfred Werner |image = Alfred_Werner.jpg|thumb |image_width = |caption = Alfred Werner |birth_date = [[December 12]], [[1866]] |birth_place = [[Mulhouse]], [[Alsace]] |residence = |nationality = [[Switzerland]] |death_date = {{death date and age| 1919|11|15|1866|12|12 }} |death_place = |field = [[Inorganic chemistry]] |work_institution = [[University of Zurich]] |alma_mater = [[University of Zurich]] |doctoral_advisor = [[Arthur Rudolf Hantzsch]], [[Marcellin Berthelot]] |doctoral_students = |known_for = configuration of [[transition metal]] complexes |prizes = [[Image:Nobel prize medal.svg|20px]] [[Nobel Prize for Chemistry]] (1913) |religion = |footnotes =. }} '''Alfred Werner''' ([[December 12]], [[1866]] - [[November 15]], [[1919]]) was a [[Switzerland|Swiss]] [[chemistry|chemist]] who was a professor at the [[University of Zurich]]. He won the [[Nobel Prize in Chemistry]] in 1913 for proposing the [[octahedral geometry|octahedral]] configuration of [[transition metal]] complexes. Werner developed the basis for modern [[coordination chemistry]]. He was the first inorganic chemist to win the Nobel prize, and the only one prior to 1973. He was born in 1866 in [[Mulhouse]], [[Alsace]] (which was then part of [[France]], but which was annexed by [[Germany]] in 1871). He went to Switzerland to study chemistry at [[Zurich]] where he obtained his [[doctorate]] in 1890. After postdoctoral study in [[Paris]], he returned to Zurich to teach in 1892, and became a professor as well a Swiss citizen in 1895. ==Coordination chemistry== In 1893, Werner was the first to propose correct structures for coordination compounds containing [[Complex (chemistry)|complex ions]], in which a central transition metal atom is surrounded by neutral or anionic [[ligands]]. For example, it was known that cobalt forms a "complex" with formula CoCl<sub>3</sub>•6NH<sub>3</sub>, but the nature of the association indicated by the dot was mysterious. Werner proposed the structure [[Cobalt(III) hexammine chloride|<nowiki>[</nowiki>Co(NH<sub>3</sub>)<sub>6</sub><nowiki>]</nowiki>Cl<sub>3</sub>]], with the Co<sup>3+</sup> ion surrounded by six NH<sub>3</sub> at the vertices of an octahedron. The three Cl<sup>-</sup> are dissociated as free ions, which Werner confirmed by measuring the [[electrical conductivity]] of the compound in aqueous solution, and also by chloride anion analysis using precipitation with [[silver nitrate]]. Later, [[magnetic susceptibility]] analysis was also used to confirm Werner's proposal for the chemical nature of CoCl<sub>3</sub>•6NH<sub>3</sub>. For complexes with more than one type of ligand, Werner succeeded in explaining the number of [[isomers]] observed. For example, he explained the existence of two isomers of "Co(NH<sub>3</sub>)<sub>4</sub>Cl<sub>3</sub>", one green and one purple. Werner proposed that these are two [[Octahedral molecular geometry#Isomerism|geometric isomers]] of formula [Co(NH<sub>3</sub>)<sub>4</sub>Cl<sub>2</sub>]Cl, with one Cl<sup>-</sup> ion dissociated as confirmed by conductivity measurements. The Co atom is surrounded by four NH<sub>3</sub> and two Cl ligands at the vertices of an octahedron. The green isomer is "trans" with the two Cl ligands at opposite vertices, and the purple is "cis" with the two Cl at adjacent vertices. Werner also prepared complexes with [[optical isomers]], and in 1914 he reported the first synthetic [[Chirality (chemistry)|chiral]] compound lacking carbon, known as [[hexol]] with formula [Co(Co(NH<sub>3</sub>)<sub>4</sub>(OH)<sub>2</sub>)<sub>3</sub>]Br<sub>6</sub>. ==Nature of valence== Before Werner, chemists defined the [[Valence (chemistry)|valence]] of an element as the number of its bonds without distinguishing different types of bond. However in complexes such as [Co(NH<sub>3</sub>)<sub>6</sub>]Cl<sub>3</sub> for example, Werner considered that the Co-Cl bonds correspond to a "primary" valence of 3 at long distance, while the Co-NH<sub>3</sub> bonds which correspond to a "secondary" or weaker valence of 6 at shorter distance. This secondary valence of 6 he referred to as the [[coordination number]] which he defined as the number of molecules (here of NH<sub>3</sub>) directly linked to the central metal atom. In other complexes he found coordination numbers of 4 or 8. On these views, and other similar views, in 1904 [[Richard Abegg]] formulated what is now known as [[Abegg's rule]] which states that that the difference between the maximum positive and negative [[Valence (chemistry)|valence]] of an [[chemical element|element]] is frequently eight. This rule was used later in 1916 when [[Gilbert N. Lewis]] formulated the “[[octet rule]]” in his [[cubical atom]] theory. Today Werner's primary valence corresponds to the oxidation state, and the secondary valence is always called coordination number. The Co-Cl bonds (in the above example) are now classed as ionic, and each Co-N bond is a [[coordinate covalent bond]] between the [[Lewis acid]] Co<sup>3+</sup> and the [[Lewis base]] NH<sub>3</sub>. ==External links== * [http://nobelprize.org/chemistry/laureates/1913/werner-bio.html Biography at Nobelprize.org] * [http://www.angelfire.com/ms3/my-page/www/press-werner.html The Nobel Prize in Chemistry 1913] - short article about his work on the linkage of atoms in molecules by which he has thrown new light on earlier investigations and opened up new fields of research especially in inorganic chemistry. * [http://www.angelfire.com/ultra2/ghbdtn/2/werner-bio.html Alfred Werner – Biography]. ==References== *{{cite journal | title = Alfred Werner's Inorganic Counterparts of Racemic and Mesomeric Tartaric Acid: A Milestone Revisited | author = W. Gregory Jackson, Josephine A. McKeon, Silvia Cortez | journal = [[Inorg. Chem.]] | volume = 43 | issue = 20 | pages = 6249–6254 | year = 2004 | url = | doi = 10.1021/ic040042e }} *{{cite journal | title = Alfred Werner Revisited: The Coordination Chemistry of Anions | author = Kristin Bowman-James | journal = [[Acc. Chem. Res.]] | volume = 38 | issue = 8 | pages = 671–678 | year = 2005 | url = | doi = 10.1021/ar040071t S0001-4842(04)00071-8 }} <br>{{Nobel Prize in Chemistry Laureates 1901-1925}} {{BD|1866|1919|Werner, Alfred}} [[Category:Alsatian Germans]] [[Category:Nobel laureates in Chemistry]] [[Category:Swiss Nobel laureates]] [[Category:ETH Zurich faculty]] [[Category:People associated with the University of Zurich]] [[Category:Swiss chemists]] [[Category:People from Alsace-Lorraine]] [[Category:People from Mulhouse]] [[ar:ألفرد فيرنر]] [[bs:Alfred Werner]] [[bg:Алфред Вернер]] [[ca:Alfred Werner]] [[cs:Alfred Werner]] [[de:Alfred Werner]] [[es:Alfred Werner]] [[eo:Alfred Werner]] [[fr:Alfred Werner]] [[gd:Alfred Werner]] [[hr:Alfred Werner]] [[io:Alfred Werner]] [[id:Alfred Werner]] [[it:Alfred Werner]] [[he:אלפרד ורנר]] [[sw:Alfred Werner]] [[nl:Alfred Werner]] [[ja:アルフレート・ヴェルナー]] [[oc:Alfred Werner]] [[pl:Alfred Werner]] [[pt:Alfred Werner]] [[ro:Alfred Werner]] [[ru:Вернер, Альфред]] [[sk:Alfred Werner]] [[sr:Алфред Вернер]] [[fi:Alfred Werner]] [[sv:Alfred Werner]] [[zh:阿尔弗雷德·维尔纳]]